This is a straw man and an ad hominem fallacy. Not all
conspiracy theorists believe in the same things, nor does believing in
aliens invalidate their arguments on other theories. The only thing
linking these things is that they are all perceived to be conspiracy
theories. Each should be evaluated on its own merits.However, if a theorist bases their beliefs on poor
argumentation, then other conspiracy theorists may want to distance
themselves from him/her or question that theorist's ability to support
their own ideas. Many such people are accused of being deliberately
planted to discredit other theories, a technique called the 'poisoned
well'. The media then proceeds to discredit an entire investigative
movement based on a few silly theories - a strawman attack.When the media lumps anybody who doesn't trust the
government version of 9-11 into the category of flat earthers and
holocaust deniers, any real conspiracy there might have been is given
the ultimate defense. Namely, a pre-emptive, universal ad hominem on
anyone who would dare talk about it publicly, the archetypal 'tin foil
hatter'.